For personnel working in harsh environments, monitoring their physical condition during their work is extremely important. For example, heat spasms or heat flares which are also known as heatstroke may lead to life-threatening dangers when the condition occurs in the field and accompanied by dangerous work. One particular example relates to firefighting activities, firefighters are required to wear protective equipment such as a fireproof suits in addition to carrying various pieces of equipment such as a tank and work in high temperature environments close to flames. Furthermore, because of the nature of the fireproof suits, heat is prone to stay in the fireproof suits and firefighters are thus more likely to be at risk for heatstroke. Moreover, firefighters are more likely to engage in activities that can push them beyond their physical limits. In light of the above, there has been a need for detecting and reporting when the firefighters are at a high risk of heatstroke.
One prior art document discloses, for example, an ear plug-type alarm system as proposed in Patent Document 1. However, because it is an ear plug-style system, there are inherent problems most notably of which is that it interferes with the hearing of the firefighters. Furthermore, with regard to firefighting activities, the ear plug-type alarm system may not be durable enough for such a harsh environment.
In Patent Document 2, a method has been proposed in which information detected by a temperature sensor is transmitted to an external module via a communication means, and the external module determines whether the risk of heatstroke. However, this method also contains problems particularly that the alarm system may not operate normally if the firefighters are in a building or in a basement and communication cannot be ensured.
A system for detecting heat stress in firefighting activities has been proposed in Patent Document 3. However, this system is also flawed because heat stress is measured at the head and there is a concern that the firefighter's activities may be hindered. Additionally, the alarm system may not work normally when the head protection equipment is removed.